The construction and assembly of a wide variety of equipment, including aircraft, ships, ground vehicles, test equipment and other equipment, frequently entails the fabrication of holes and other features in structural members and the installation of fasteners through such holes to assemble structural members. Holes must often be fabricated which extend through two or more layers of structural material, such as through multiple layers in an aircraft skin, or through two or more structural members, such as through an aircraft skin and an underlying stiffening rib. It is often important that such holes and features be located accurately relative to other features and that such holes and features be fabricated precisely so that the structural integrity of the equipment is maintained.
It is conventional in the construction and assembly of equipment with many features for complex sets patterns of holes and other features to be fabricated with the aid of a tooling fixture, such as a drill plate. If, for example, multiple identical assemblies must be constructed, such as for multiple wing assemblies on an aircraft production line, a durable, reusable drill plate in which a pattern of holes or features has been formed may be used as a template by which holes and features in each assembly may be fabricated. The use of a tooling fixture such as a drill plate helps to ensure that all holes in the assembly are precisely located relative to one another. The location of the hole pattern on the structure relative to other features of the structure (i.e. the "float" of the hole pattern over the structure) can be controlled by providing tooling points on the structure which mate to drill plate tooling points and which fix the location of the hole pattern relative to the remainder of the structure.
When holes must be fabricated which extend through two or more layers of structural material, such as through multiple layers in an aircraft skin, or through two or more structural members, such as through an aircraft skin and an underlying stiffening rib, there is often a tendency for the layers or members to separate slightly during fabrication operations. For example, when holes through multiple layers are fabricated with a drill, the forward pressure exerted by the drill operator on the assembly tends to force the layers apart as the drill passes through successive layers. When layers separate during fabrication, burrs and chips developed from the structural material by the fabrication tool may lodge between layers. Interlayer burrs and chips may prevent proper fastener attachment or pose other structural integrity problems.
The problem of separation of layers or members during fabrication is conventionally addressed by the use of wedgelocks, such as Monogram Aerospace Fasteners Tool Number TD391N1-X. Wedgelocks clamp the tooling plate firmly against the multiple layers or structural members by providing two or more flexible arms which are inserted through collinear holes in the tooling plate and the structural assembly and which engage the back side of the structural assembly by way of a shoulder at the tip of each arm. The opposing end of the wedgelock arms screws into a wedgelock head on the front side of the tooling plate, enabling an operator to adjust the clamping force of the wedgelock by twisting the wedgelock head. Wedgelocks are typically spaced every several inches across a tooling plate to evenly clamp the structural assembly to the tooling plate.
Conventional wedgelocks solve to some extent the problem of the separation of layers or members during the fabrication of holes to be drilled through flat surfaces and structural layers or members of uniform thickness, but curved surfaces and varying thicknesses present fabrication difficulties which conventional wedgelocks are unable to adequately overcome. In particular, conventional wedgelocks apply force to the back side of the structural assembly to pull the assembly toward the tooling plate, but the presence of curved surfaces and thickness variations will result in contact between the back side of the tooling plate and the front side of the structural assembly at only a few points. In those areas where the structural assembly is not drawn forcibly against the tooling plate by the conventional wedgelock, drilling or other fabrication operations may cause separation of layers or members, may introduce burrs or chips between layers, and may therefore result in irregular holes and fastener installation problems. The separation of layers results because the conventional wedgelock provides no force to clamp the layers or members together in those areas where the structural assembly is not drawn forcibly against the tooling plate because of surface curvature or thickness variations.
The introduction of burrs or chips between layers or members may be a significant problem during construction and assembly operations. If burrs and chips are not removed, there may be movement between structural parts during fastener installation. Burr and chip removal may entail expensive and time-consuming disassembly of structural assemblies.
Moreover, the diameter of the arms of a conventional wedgelock is often considerably smaller than diameter of the wedgelock alignment hole in the tooling plate to be clamped to the structural assembly, and misalignment may therefore result. There is thus a need for a tool which enables more precise alignment of tooling plates having larger wedgelock alignment hole diameters.
While conventional wedgelocks may adequately clamp a tooling plate to a flat and uniform multi-layer or multi-element assembly during fabrication operations requiring moderate hole location accuracy, there is a need for a tool which can enable more accurate tooling plate alignment and which can prevent separation of layers and elements in structural assemblies with curved surfaces and varying thicknesses during fabrication operations.